Technical Field
The present invention relates to a method of treating a zirconia containing ceramic surface using laser ablation and application of a N2 assist gas.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Stabilized zirconia is widely used in industry due its superior properties such as high wear and temperature resistances, and low thermal conductivity. Some applications of stabilized zirconia include thermal barrier coating in jet and diesel engines to allow operation at higher temperatures, sensor technologies for oxygen sensing, and fuel cell membranes operating at high temperatures. See D. S. Almeida, C. A. A. Cairo, C. R. M. Silva, M. C. A. Nono, Thermal barrier coating by electron beam-physical vapor deposition of zirconia co-doped with yttria and niobia, J. Aerosp. Technol. Manag., Sāo José dos Campos 2 (2)(2010) 195-202; B. Benammar, Design and assembly of miniature zirconia oxygen sensors, IEEE Sens. J. 4 (1) (2004) 3-8, and V. S. Silva, B. Ruffmann, H. Silva, V. B. Silva, A. Mendes, L M. Madeira, S. Nunes, Zirconium oxide hybrid membranes for direct methanol fuel cells-evaluation of transport properties, J. Membr. Sci, 284 (1-2) (2006) 137-144, each incorporated herein by reference in their entirety. The surface characteristics of stabilized zirconia, including hardness and hydrophobicity, can be improved further through various surface treatment methods. Since biomimetic characteristics of surfaces received great attention in industry, various methods have been developed in this regard. Some of these methods include phase separation, electrochemical deposition, template method, emulsion, plasma method, crystallization control, chemical vapor deposition, sol-gel processing, lithography, electrospinning, and solution immersion. See J. T. Han, X. R. Xu, K. W. Cho, Diverse access to artificial superhydrophobic surfaces using block co-polymers, Langmuir 21 (15) (2005) 6662-6665; N. J. Shirtcliffe, G. McHale, M. I. Newton, G. Chabrol, C. C. Perry, Dual-scale roughness produces unusually water-repellent surfaces. Adv. Mater. 16 (21) (2004) 1929-1932; H. S. Hwang, S. B. Lee, I. Park, Fabrication of Raspberry-Like superhydrophobic hollow silica particles. Mater, Lett. 64 (201 (2010) 2159-2162; T. Yang, H. Tian, Y. Chen, Preparation of superhydrophobic silica films with honeycomb-like structure by emulsion method, J. Sol-Gel Sci. Technol. 49 (2) (2009) 243-246; H. Kinoshita, A. Ogasahara, Y. Fukuda, N. Ohmae, Superhydrophobic/superhydrophilic micropatterning on a carbon nanotube film using a laser plasma-type Hyperthermal atom beam facility, Carbon 48 (15) (2010) 4403-4408; Z. G. Guo, J. Fang, J. C. Hao, Y. M. Liang, W. M. Liu, A novel approach to stable superhydrophobic surfaces, Chem. Phys. Chem. 7 (8) (2006) 1674-1677; K. K. Lau, J. Bico, K. B. K. Teo, M. Chhowalla, G. A. J. Amaratung, W. I. Milne, G. H. McKinley, K. K. Gleason, Superhydrophobic carbon nanotube forests, Nano Lett. 3 (12) (2003) 1701-1705; S. S. Latthe, H. Imai, V. Ganesan, A. V. Rao, Super-hydrophobic silica films by sol-gel co-precursor method, Appl. Surf. Sci. 256 (1) (2009) 217-222; R. Furstner, W. Barthlott, C. Neinhuis, P. Walzel, Welting and self-cleaning properties of artificial superhydrophobic surfaces, Langmuir 21 (3) (2005) 956-961; M. Ma, Y. Mao, M. Gupta, K. K. Gleason, G. C. Rutledge, Superhydrophobic fabrics produced by electrospinning and chemical vapor deposition, Macromolecules 38 (23) (2005) 9742-9748; and X. Zhang, Y. Guo, P. Zhang, Z. Wu, Z. Zhang, Superhydrophobic CuO@Cu2S nanoplate vertical arrays on copper surfaces. Mater. Lett 64 (10) (2010) 1200-1203, each incorporated herein by reference in their entirety. However, transforming low-surface-energy materials into textured surfaces is one of the techniques which can be used to enhance the hydrophobicity of the surfaces. Laser surface texturing through a controlled ablation offers considerable advantages over the conventional texturing methods. Some of these advantages include high speed operation, high precision, local treatment, and low cost. However, the presence of the mixed regime of melting and ablation at the surface modifies the surface texture, which alters the wetting state of the surface. In addition, high stress levels are developed in laser treated region because of the high temperature gradients, which are formed in the irradiated region due to high heating and cooling rates. The fracture toughness of the surface also reduces due to microhardness enhancement at the surface after the treatment process. Consequently, investigation of laser treatment of zirconia surface for improved hydrophobicity and assessment of the residual stress and the fracture toughness in the treated region becomes essential.
Considerable research has been carried out to examine laser treatment of zirconia surfaces. Laser surface treatment of partially stabilized zirconia for biomedical applications was presented by Hao and Lawrence. See L. Hao, J. Lawrence, The adsorption of human serum albumin (HSA) on CO2 laser modified magnesia partially stabilized zirconia (MgO—PSZ). Colloids Surf. B: Biointerfaces 34 (2) (2004) 87-94, incorporated herein by reference in its entirety. They observed that the thickness of the adsorbed human serum albumin decreased as the polar surface energy of the magnesia partially stabilized zirconia increased. Laser treatment of zirconia surfaces was examined by Chwa and Ohmori. See S. O. Chwa, A. Ohmori, The influence of surface roughness of sprayed zirconia coatings on laser treatment. Surf Coat. Technol. 148 (1) (2001) 38-95, incorporated herein by reference in its entirety. They indicated that the surface roughness of zirconia prior to the laser treatment was important, since the melt depth of the polished coatings was approximately half of the rough coatings when treated at the same power density. Laser surface treatment of plasma-sprayed yttria-stabilized zirconia coatings was investigated by Pinto et al. See M. A. Pinto, W. R. Osorio, C. R. P. Lima, A. Garcia, M. C. F. Ierardi, Laser surface treatment of plasma-sprayed yttria-stabilized zirconia coatings, Revista de Metalurgia (Madrid), Spec. (2005) 154-159, incorporated herein by reference in its entirety. They showed that the microstructure of the treated layer presented a cellular structure which grew perpendicular to the surface and the micrographs depicted small cracks and the absence of pores. Laser surface nitriding of yttria stabilized tetragonal zirconia was studied by Kathuria. See Y. P. Kathuria, Laser surface nitriding of yttria stabilized tetragonal zirconia, Surf. Coat. Technol. 201 (12) (2007) 5865-5869, incorporated herein by reference in its entirety. The findings revealed that the transformation of the t-ZrO2 exhibited the typical yellow-gold color of ZrN with high hardness at the surface. Laser surface modification of plasma sprayed yttria stabilized zirconia coatings was examined by Shankar and Mudali. See A. R. Shankar, U. K. Mudali, Laser surface modification of plasma sprayed yttria stabilized zirconia coatings on type 316L stainless steel, Surf. Eng. 25 (3) (2009) 241-248, incorporated herein by reference in its entirety. They observed that a distinct interface separating fine and coarse grains took place at all scan speeds and the microhardness of the glazed surface improved considerably. Laser treatment of a zirconia surface and morphological and microstructural changes in the treated layer was investigated by Daniel et al. See C. Daniel, B. L. Armstrong, B J. Y. Howe, N. B. Dahotre, Controlled evolution of morphology and microstructure in laser interference-structured zirconia, J. Am. Ceram. Soc. 91 (7) (2008) 2138-2142, incorporated herein by reference in its entirety. They showed that the surface morphology closely followed the microperiodic heat treatment provided by the interfering laser beams and the pore size distribution within the periodic surface morphology ranged from a few nanometers to a maximum of half of the periodic line distances. Laser ablation characteristics of yttria-doped zirconia in nanosecond and femtosecond regimes were studied by Heiroth et al. See S. Heiroth, J. Koch, T. Lippert, A. Wokaun, D. Gunther, F. Garrelie, M. Guillermin, Laser ablation characteristics of yttria-doped zirconia in the nanosecond and femtosecond regimes, J. Appl. Phys. 107 (1) (2010) 014908-014918, incorporated herein by reference in its entirety. They showed that femtosecond pulses prevented the exfoliation of micron-sized fragments, but result invariably in a pronounced ejection of submicron particles. Thermal fatigue properties of laser treated surfaces were investigated by Aqida et al. See S. N. Aqida, F. Calosso, D. Brabazon, S. Naher, M. Rosso, Thermal fatigue properties of laser treated steels. Int. J. Mater. Form. 3 (Supp. 1) (2010) 797-800, incorporated herein by reference in its entirety. They observed that carbide and oxide compounds were formed on the laser treated surface after the thermal fatigue test. Thermal stability of laser treated die material for semi-solid metal forming was examined by Aqida et al. See S. N. Aqida, M. Maurel, D. Brabazon, S. Naher, M. Rosso, Thermal stability of laser treated die material for semi-solid metal forming. Int. J. Mater. Form. 2 (Suppl. 1) 2009) 761-764, incorporated herein by reference in its entirety. The findings revealed that crystallization in the glazed zone increased as the annealing temperature increased and the micro-hardness decreased due to local crystallization at the surface.
Hydrophobicity of the substrate surfaces can be improved through forming fine poles at the surface during laser texturing. See B. S. Yilbas, M. Khaled, N. Abu-Dheir, N. Ageeli, S. Z. Furquan, Laser texturing of alumina surface for improved hydrophobicity, Appl. Surf. Sci. 286 (2013) 161-170, incorporated herein by reference in its entirety. Modification of wetting properties of laser-textured surfaces was studied by Bayer et al. See I. S. Bayer, F. Brandi, R. Cingolani, A. Athanassiuu, Modification of wetting properties of laser-textured surfaces by depositing triboelectrically charged Teflon particles, Colloid Polym. Sci. 291 (2) (2013) 367-373, incorporated herein by reference in its entirety. They showed that superhydrophobic surfaces could be achieved through Teflon deposition at the laser textured surface. Bacterial retention on superhydrophobic laser ablated titanium surfaces was investigated by Fadeeva et al. See E. Fadeeva, V. K. Truong, M. Stiesch, B. N. Chichkov, R. J. Crawford, J. Wang, E. P. Ivanova, Bacterial retention on superhydrophobic titanium surfaces fabricated by femtosecond laser ablation, Langmuir 27 (6) (2011) 3012-3019, incorporated herein by reference in its entirety. They indicated that the untreated surface was hydrophobic, whereas the laser-treated surface became superhydrophobic and the attached bacterial cells were found to be below the estimated lower limit. Laser patterning of steel surfaces for improved hydrophobicity was examined by Luo et al. See B. H. Luo, P. W. Shum, Z. F. Zhou, K. Y. Li, Preparation of hydrophobic surface on steel by patterning using laser ablation process, Surf. Coat. Technol. 204 (2010) 1180-1185, incorporated herein by reference in its entirety. They showed that when the laser produced pattern was set at 25 μm spacing, the contact angle of the surface could be increased to about 130°, compared to the 68.5° corresponding to a plain smooth steel surface with Ra≦0.01 μm.
The surface energy of zirconia can be modified by a laser heating at the surface, which may further improve surface hydrophobicity. See S. Norouzian, M. M. Larijani, R. Afzalzadeh, Effect of nitrogen flow ratio on structure and properties of zirconium nitride films on Si(100) prepared by ion beam sputtering, Bull. Mater Sci. 35 (5) (2012) 885-887, incorporated herein by reference in its entirety. Although laser treatment of zirconia surfaces has been examined previously, modifying and investigating the surface hydrophobicity has not been reported. See B. S. Yilbas, S. S. Akhtar, A. Matthews, C. Karatas, Laser remelting of zirconia surface: investigation into stress field and microstructures. Mater. Manuf. Process, 26 (10) (2011) 1277-1287; and B. S. Yilbas, S. S. Aktar, C. Karatas, Laser controlled melting of pre-treated zirconia surface, Appl. Surf. Sci. 257 (15) (2011) 6912-6918, each incorporated herein by reference in their entirety.
In view of the forgoing, the objective of the present invention is to provide a method of treating a zirconia containing ceramic surface using laser ablation and application of a N2 assist gas to increase surface hydrophobicity.